For over a hundred years, piston engines have been utilized to convert the energy in hydrocarbon based fuel to useful power outputs. Typically, these engines have incorporated variable volume combustion chamber or chambers using a cycle having an intake portion, a compression portion, an expansion portion and an exhaust portion. The variable volume combustion chamber is most typically defined by a reciprocating piston in a cylinder bore and connected by appropriate mechanical devices to a crankshaft or other rotary output component. The engines may be two cycle or four cycle according to the need.
The consideration of efficiency has always been important but with advances in regulatory limits during the last twenty years, reducing emissions, including nitrous oxides, has become exceedingly important. The usual steps for combustion management to minimize emissions typically decrease efficiency of the engine. In the case of the compression ignition or diesel engine cycle, the need to reduce oxides of nitrogen requires significant alteration to the operating conditions which tends to decrease the otherwise outstanding efficiency of such an engine type.
A number of attempts have been made to increase efficiency by fully utilizing the energy available in such engines through power extraction devices in the exhaust of the engine. Such power extraction devices may be a turbo supercharger (turbocharger) which receives the exhaust from the engine and drives a compressor connected to the engine intake by appropriate manifolds. The heat of pressurization by the compressor may be supplied to an intercooler or aftercooler to reduce the temperature of the gases flowing into the engine and thus increase the density of the mixture. Another energy extraction device is found in a power turbine which may be used to supply additional power to the engine output via an appropriate mechanical connection or may be used to drive a turbo generator supplying electrical energy for accessory and other loads.
While some systems have been proposed to provide a separate exhaust for different power extraction devices, such systems do not provide a system having a maximum efficiency.
Accordingly, what is needed in the art is a prime mover system incorporating an internal combustion engine and power extraction devices which more efficiently utilize the energy available from the internal combustion engine.